(i) Field of the Invention
The present invention relates generally to cleanup of oil spills in a marine environment and, more particularly, to bioremediation or biological removal of floating oil through biodispersion.
(ii) Description of Related Art
Pollution of rivers, streams, harbors, bays, beaches and the open sea by hydrocarbon oil has increased tremendously in recent years. It is difficult to assess the quantity of polluting oil in any aqueous environment, since the oil generally transforms into the following four states on encountering water. These are a) as film on water, b) as solution in dissolved state, c) as emulsion of oil in water and d) in the form of tar balls. It is possible that only laser acoustic instruments may provide absolute values for the thickness of oil.
It has been reported that at least 10% of the volume of oil being transported through tankers and super tankers finds its way to estuaries and harbors polluting these environments. The volume of oil discharged through handling and transportation in addition results in a release of millions of gallons of oil into the sea. Although a major oil spill may occur in mid-ocean, actual harmful effects are felt only in the coastal regions and estuaries. The pollution of water by oil therefore, is not regarded as an oceanic problem but a coastal hazard.
Presently only two methods are generally regarded as safe in removing floating oil from any environment. One is physical removal of floating oil employing mechanical skimmer and suction devices of various types. The second one is bioremediation of contaminating oil. Although mechanical skimmers are effective in removing oil after oil spills of major or minor nature, the mechanical process does not remove all the oil completely and the residual oil once again finds its way to coastal regions or estuaries and beaches.
Bioremediation has been recognized as a technology to combat oil pollution through an environmentally friendly technique. The technology has been employed for shoreline clean up in Alaska after the accidental spill of 11 million gallons of crude oil spilled from the tanker EXXON VALDEZ in 1989. Results of massive experiments undertaken for the clean up of the shore line along the coast of Alaska by the representatives of U.S. Environmental Protection Administration (E.P.A) and those of EXXON Co. Houston have been published by both the U.S. E.P.A. and EXXON in 1991 and 1992, respectively. Thus a technology for shoreline clean up through bioremediation has been demonstrated which even today remains successful in a limited way.
Problems in harbors and ports are of a different nature and can not be subjected to the same technology. Bioremediation by addition of oil degrading microbes is often promoted as a treatment of floating spills, but this approach has not met with any documented success (Prince, 1998). Thus, the treatment for a floating oil spill requires a totally new approach.